Well, I just finished building my very own 18x36 in ground vinyl lined pool. I hired out only the excavation, auto pool cover, and finished cement. The poolcrete about killed me, lost 15lbs and my forearms look like popeye the sailor.

Looking to join a great forum for learning and help.

First question is how do I figure out my water capacity in gallons? I have an 18x36 with 2' radius and 3ft shallow end about 8ft long, and then drops to a 9ft deep end?

Second would be getting my pool chem's in order. I used the Taylor K-2005 kit
FC=~5 (highest red on chart)
TC=~5 (almost looks same color)
PH=7.2
TA=140
CH= 120
CYA=35

My AutoPilot is on power cell =2 and at 3000 salt and set to 30K gallon pool. Running my pump 6 hours in the day and 5 more at night. Water is 80F

Water looks clear, but my chemical numbers don't look right above. Shouldn't my Calcium hardness be much higher? or is it ok?

My TA looks high also at 140, however my ph is 7.2. Should I add something?

And what about the chlorine levels?

Still reading and learning about the BBB. Didnt see anything on lowering TA without touching PH.

Your chlorine level looks good! If FC and TC are the same, that means you have no CC's.

What type of kit are you using to test? If your CC's get to .3 or above you need to shock.

Since you are vinyl - you don't want to let your pH get much lower. You need to raise your pH before you even attempt to lower your TA. You use muriatic acid then to lower your pH back down to 7.2 which will also lower your TA, then aerate your pool to bring the pH back up to the high number of the pH range and treat again with muriatic acid. It can take several treatments to lower your TA. 140 isn't terrible, though.

You don't need to worry about calcium in a vinyl pool. It's fine where it is.

You can probably turn the AutoPilot down to power level 1. Your FC is high, so either turn down the power level or reduce the percentage.

Otherwise, your numbers look tolerable to me, not ideal but perfectly acceptable. Your TA is a little higher than the ideal, but in a vinyl pool with a farily low calcium level that shouldn't cause any problems. There is no reason to add calcium to a vinyl pool, unless one of your warranties requires it. Also, your PH is a little low. You don't want the PH going down below there but there isn't any rush to get it higher (since you aren't using trichlor or dichlor). The SWG will aerate the pool a bit and bring the PH up in the course of normal operations, so basically you are fine for now.

It won't be too hard to guesstimate, but since it is a new pool, look in the papers that came with it. Maybe on the dig sheet you used for the excavation. My kit is by Kafko and the drawings tell a lot of useful information like perimeter, area, and capacity in gallons. If you excavated according to the specs the listed capacity should be very accurate.

If your water looks great try lowering your pump run time an hour and see what happens over the next few weeks. Many people say that you should get one turn over of your water each day, but calculating that is difficult. If you want to try the calculations see this thread. I figure that what really matters is how your water looks.

You shock when the water is green or when you have combined chlorine or when you can't hold any chlorine level. If you keep the chlorine level steady based on the best guess chart and your pool gets direct sunlight none of that should happen (except perhaps when you open each season).

From my work Computer I cannot attach an Adobe cheat sheet for figuring out Gallons but go to the Hayward Pump Sizing site or go to the home page and click on product , pumps, inground and sizing. A PDF will open and you can compute your volume.

This will not give you an exact amount but will give you a very good estimate.

Based on what I am reading I would guess ~29,160 gallons not including the radius.

BigDave, congrats on the pool! My quick estimate is ~27,500 on gals. Do you know how much salt was added to the pool to get to 3000 ppm, the salt will give you a very! good estimate of the gallonage, compare the amt of salt added to the chart in your owners manual and you've got the gallonage just about dialed in!! Most SWCG manufaturers recommend 50 - 80 ppm cya (i cheat and add 1 lb/ 100 lbs salt to get to 30- 40 ppm) I'm not 100% convinced, but have been adding a lb or 2 extra to the SWCG pools, I don't fully understand the chemistry, so am slowly bringing the cya level up.
God willin' and the creek don't rise, this is somewhat helpful

Thanks to All, appreciate the time taken for responses. This is going to be a fun site.

Manufacture just replied after almost a month and said 25875 gallons. Sure sounds low based off everyones input above. I also predicted around 29.5k based off other sites calculations????

Based off the 1 hour for every 10 degree method, I may be able to reduce my pump time by a couple hours. From Jasonlion's response, I'll try an hour reduction tonight and three or four days later try another if the water still looks good.

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